That's fine for a flag/pulse type signal that has a 'default' value most of the time. Particularly if it is only sparsely set to a non-default in the if/then/else tree. Which is most likely the case for a signal with a name like that.
Of course if this was being used as a state variable/bit, you don't want to assign a value by default since the whole point of state variables is to hold on to what they had last cycle. And a default "A <= A;" is unnecessary since A already keeps its old value unless there's an "A <= B;" somewhere in the if/then/else.
also, rising_edge(clk) is a little more modern than clk'event and clk='1'.
Otherwise, fairly good style. and kudos for actually labeling the clocked process.